A commonly used type of spring contact for circuit boards comprises a platelike spring contact having legs extending therefrom, which are inserted into holes in a circuit board, the holes being located such that the platelike member covers, and is in spaced relationship to, a first conductor on the circuit board. When the legs are soldered to second conductors on the circuit board, a circuit path can be established between the first and second conductors by flexing the platelike member towards the circuit board until it moves against the first conductor. The contact member usually forms part of a switch which is closed by simply pressing on the contact member and when finger pressure is removed, the platelike member returns to its normal position and the circuit path is broken. It is common to solder the legs of contact devices of this type to the second conductors on the circuit board, although it is known to rely entirely on mechanical fastening of the contact device to the circuit board, as shown, for example, in U.S. Pat. No. 4,136,269.
Most, if not all, of the spring contact devices discussed above are such that the first conductor, which is engaged by the platelike contact member, must be on one side of the circuit board and the second conductors must be on the other side of the circuit board. When the device is assembled to the board by inserting the legs through holes in the circuit board, the legs can then be soldered to the second conductors on the underside of the circuit board.
It would be desirable to provide a spring contact device which would be capable of use on a circuit board having all of its conductors on one surface thereof, in other words, a so-called one-sided circuit board. Circuit boards having conductors on only one surface thereof can usually be produced at a lower cost than circuit boards having conductors on both surfaces and are therefore preferred in the manufacture of many articles which must be produced at a minimum overall cost.
The invention is also directed to the achievement of an improved solderless spring contact member of the general type discussed above which can be assembled to the circuit board by a simple insertion operation and which will be placed in contact with conductors on the circuit board as the result of the assembly operation. The present invention is further directed to the achievement of a contact device which will prove to be reliable and durable after installation on the circuit board.
A spring metal contact member in accordance with the invention comprises a stamped and formed device of thin resilient material, such as stainless steel, having a platelike portion from which a pair of mounting legs extend, which are dimensioned to enter circuit board holes. Each mounting leg comprises an elongated strip which has been reversely formed to provide first and second side-by-side straight portions, a reversely formed bight portion, and a free end spring portion. The first leg is integral with and extends from the platelike section of the device and the first and second legs are connected to each other by an intermediate bight portion. The spring arm portion extends laterally from the second leg so that when the legs are inserted into the circuit board holes, the spring arms then extend laterally to conductors on the circuit board. During insertion, the bight portion of each leg and parts of each straight portion of each leg are severely plastically deformed and caused to move laterally of their original positions. This deformation of lower portions of the legs, coupled with other features of the legs, establishes an interference fit of each leg and its circuit board hole so that the device is permanently assembled to the circuit board. An important feature of the invention is that when the platelike portion of the device is pressed towards the circuit board and into engagement with a first conductor on the circuit board, the forces imposed on the platelike section of the device are transmitted to the spring arm portions which are caused to slide and rub over the second conductors which they are normally disposed against. This movement of the spring arm portions has the effect of cleaning these contact surfaces immediately prior to establishment of the circuit path and thereby ensures a high degree of reliability in the operation of the device.